Organic electroluminescence device, organic electroluminescence unit, and electronic apparatus

ABSTRACT

An organic electroluminescence device includes, in order, a first electrode, a hole transport layer, an organic light-emitting layer, an electron transport layer, and a second electrode. The hole transport layer is configured by a coated film. The organic light-emitting layer is configured by a coated film. The organic light-emitting layer is made of an organic light-emitting material that has a molecular orientation degree specified by a parameter S′. The parameter S′ satisfies an inequality: 0.66&lt;S′&lt;0.75, provided that S′={(2×ko)/(ke+2ko)}. In this expression, ko denotes an extinction coefficient in a film-plane direction of the organic light-emitting layer, and ke denotes an extinction coefficient in a film-thickness direction of the organic light-emitting layer.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of Japanese Priority PatentApplication JP 2016-142275 filed on Jul. 20, 2016, and Japanese PriorityPatent Application JP 2017-004074 filed on Jan. 13, 2017, the entirecontents of both of which are incorporated herein by reference.

BACKGROUND

The disclosure relates to an organic electroluminescence device, anorganic electroluminescence unit, and an electronic apparatus.

Various organic electroluminescence units such as organicelectroluminescence displays each including an organicelectroluminescence device have been proposed, as disclosed in JapaneseUnexamined Patent Application Publications No. 2008-270770, No.2011-009205, and No. 2014-225710, for example.

SUMMARY

An organic electroluminescence unit is generally requested to have anenhanced device performance of an organic electroluminescence device.

It is desirable to provide an organic electroluminescence device havingan enhanced device performance, and an organic electroluminescence unitand an electronic apparatus that make it possible to enhance the deviceperformance of the organic electroluminescence device.

An organic electroluminescence device according to an embodiment of thedisclosure includes, in order, a first electrode, a hole transportlayer, an organic light-emitting layer, an electron transport layer, anda second electrode. The hole transport layer is configured by a coatedfilm. The organic light-emitting layer is configured by a coated film.The organic light-emitting layer is made of an organic light-emittingmaterial that has a molecular orientation degree specified by aparameter S′. The parameter S′ satisfies an inequality: 0.66<S′<0.75,provided that S′={(2×ko)/(ke+2ko)}. In this expression, ko denotes anextinction coefficient in a film-plane direction of the organiclight-emitting layer, and ke denotes an extinction coefficient in afilm-thickness direction of the organic light-emitting layer.

An organic electroluminescence unit according to an embodiment of thedisclosure is provided with a plurality of organic electroluminescencedevices. In the organic electroluminescence unit, one or more of theplurality of organic electroluminescence devices include, in order, afirst electrode, a hole transport layer, an organic light-emittinglayer, an electron transport layer, and a second electrode. The holetransport layer is configured by a coated film. The organiclight-emitting layer is configured by a coated film. The organiclight-emitting layer is made of an organic light-emitting material thathas a molecular orientation degree specified by a parameter S′. Theparameter S′ satisfies an inequality: 0.66<S′<0.75, provided thatS′={(2×ko)/(ke+2ko)}. In this expression, ko denotes an extinctioncoefficient in a film-plane direction of the organic light-emittinglayer, and ke denotes an extinction coefficient in a film-thicknessdirection of the organic light-emitting layer.

An electronic apparatus according to an embodiment of the disclosure isprovided with an organic electroluminescence unit. The organicelectroluminescence unit in the electronic apparatus has a plurality oforganic electroluminescence devices. One or more of the plurality oforganic electroluminescence devices include, in order, a firstelectrode, a hole transport layer, an organic light-emitting layer, anelectron transport layer, and a second electrode. The hole transportlayer is configured by a coated film. The organic light-emitting layeris configured by a coated film. The organic light-emitting layer is madeof an organic light-emitting material that has a molecular orientationdegree specified by a parameter S′. The parameter S′ satisfies aninequality: 0.66<S′<0.75, provided that S′={(2×ko)/(ke+2ko)}. In thisexpression, ko denotes an extinction coefficient in a film-planedirection of the organic light-emitting layer, and ke denotes anextinction coefficient in a film-thickness direction of the organiclight-emitting layer.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings are included to provide a furtherunderstanding of the disclosure, and are incorporated in and constitutea part of this specification. The drawings illustrate exampleembodiments and, together with the specification, serve to explain theprinciples of the technology.

FIG. 1 illustrates an example of a cross-sectional configuration of anorganic electroluminescence device according to a first embodiment ofthe disclosure.

(A) of FIG. 2 schematically illustrates an example of energy bandstructures of respective layers of the organic electroluminescencedevice of FIG. 1; and (B) of FIG. 2 illustrates an example of absorptionspectra of a hole transport layer and an electron transport layer in (A)of FIG. 2 as well as an example of an emission spectrum of an organiclight-emitting layer in (A) of FIG. 2.

(A) of FIG. 3 schematically illustrates an example of energy bandstructures of respective layers of an organic electroluminescence deviceof Comparative Example A; and (B) of FIG. 3 illustrates an example ofabsorption spectra of a hole transport layer and an electron transportlayer in (A) of FIG. 3 as well as an example of an emission spectrum ofan organic light-emitting layer in (A) of FIG. 3.

(A) of FIG. 4 schematically illustrates an example of energy bandstructures of respective layers of an organic electroluminescence deviceof Comparative Example B; and (B) of FIG. 4 illustrates an example ofabsorption spectra of a hole transport layer and an electron transportlayer in (A) of FIG. 4 as well as an example of an emission spectrum ofan organic light-emitting layer in (A) of FIG. 4.

FIG. 5A illustrates an example of a light emission region inside anorganic light-emitting layer.

FIG. 5B illustrates an example of the light emission region inside theorganic light-emitting layer.

FIG. 5C illustrates an example of the light emission region inside theorganic light-emitting layer.

FIG. 5D illustrates an example of the light emission region inside theorganic light-emitting layer.

FIG. 6 illustrates an example of an outline configuration of an organicelectroluminescence unit according to a second embodiment of thedisclosure.

FIG. 7 illustrates an example of a circuit configuration of a pixel inFIG. 6.

FIG. 8 is a perspective view of an example of an appearance of anelectronic apparatus provided with the organic electroluminescence unitof an embodiment of the disclosure.

FIG. 9 is a perspective view of an example of an appearance of anillumination apparatus provided with the organic electroluminescencedevice of an embodiment of the disclosure.

DETAILED DESCRIPTION

Some example embodiments of the disclosure are described below in detailwith reference to the accompanying drawings. The example embodimentsdescribed below each illustrate a specific but non-limiting preferredexample of the disclosure. Accordingly, factors such as numerical value,shape, material, components, and arrangement positions and theconnection of the components are merely examples, and are not to beconstrued as limiting to the disclosure. Therefore, among the elementsin the following example embodiments, the elements that are not recitedin a most-generic independent claim according to an embodiment of thedisclosure are each described as an optional element. It is to be notedthat the drawings are schematic diagrams, and are not necessarilyaccurate in a strict sense. Further, in the drawings, the same referencenumerals are assigned to substantially the same components, andoverlapping descriptions are omitted or simplified. It is to be notedthat the description is given in the following order.

1. First Embodiment (Organic Electroluminescence Device)

2. Second Embodiment (Organic Electroluminescence Unit)

3. Application Example (Electronic Apparatus and Illumination Apparatus)

1. First Embodiment [Configuration]

FIG. 1 illustrates an example of a cross-sectional configuration of anorganic electroluminescence device 1 according to a first embodiment ofthe disclosure. The organic electroluminescence device 1 may beprovided, for example, on a substrate 10. The organicelectroluminescence device 1 includes, for example, an organiclight-emitting layer 13, a hole transport layer 12, and an electrontransport layer 14. The hole transport layer 12 and the electrontransport layer 14 are so disposed as to interpose the organiclight-emitting layer 13 therebetween. The hole transport layer 12 may beprovided on hole-injection side of the organic light-emitting layer 13,and the electron transport layer 14 may be provided onelectron-injection side of the organic light-emitting layer 13. Theorganic electroluminescence device 1 may have a device structure ofincluding, for example, an anode 11, the hole transport layer 12, theorganic light-emitting layer 13, the electron transport layer 14, and acathode 15, in this order, from the substrate 10. The organicelectroluminescence device 1 may further include other functional layerssuch as a hole injection layer and an electron injection layer.

The substrate 10 may be, for example, a light-transmissive translucentsubstrate such as a transparent substrate, and may be, for example, aglass substrate made of a glass material. It is to be noted that thesubstrate 10 is not only limited to the glass substrate, but may also beeither a translucent resin substrate made of a translucent resinmaterial such as polycarbonate resin and acrylic resin, or a thin-filmtransistor (TFT) substrate that is a backplane of an organicelectroluminescence (EL) display unit.

The anode 11 may be provided on the substrate 10, for example. The anode11 may be a transparent electrode having translucency. For example, atransparent electrically conductive film made of a transparentelectrically conductive material such as indium tin oxide (ITO) andindium zinc oxide (IZO) may be used for the anode 11. It is to be notedthat the anode 11 is not only limited to the transparent electrode, butmay also be either an electrode made of any of aluminum (Al), silver(Ag), an aluminum alloy, and a silver alloy, for example, or areflective electrode having reflectivity. The anode 11 may also have alayered configuration of the reflective electrode and the transparentelectrode.

The hole transport layer 12 may serve to transport, to the organiclight-emitting layer 13, holes injected from the anode 11. The holetransport layer 12 may be a coated film, and may be formed by coatingand drying of a solution containing, as a solute, a hole transportingmaterial 12M. In other words, the hole transport layer 12 may includethe hole transporting material 12M. Further, the hole transportingmaterial 12M that is a solute may have an insoluble function. Theinsoluble function refers to a function in which an insoluble group suchas a cross-linking group and a thermal dissociation soluble groupundergoes chemical transformation, which is caused by irradiation withheat or ultraviolet rays, for example, or by a combination thereof, thusallowing the chemically transformed group to be insoluble to an organicsolvent or water. Accordingly, the hole transport layer 12 may be aninsolubilized hole transport layer.

The hole transport layer 12 may be made of the hole transportingmaterial 12M having the insoluble function. Examples of the holetransporting material 12M that is a raw material, i.e., a material ofthe hole transport layer 12 may include an arylamine derivative, atriazole derivative, an oxadiazole derivative, an imidazole derivative,a polyarylalkane derivative, a pyrazoline derivative and a pyrazolonederivative, a phenylenediamine derivative, an amino-substituted chalconederivative, an oxazole derivative, a styrylanthracene derivative, afluorenone derivative, a hydrazone derivative, a stilbene derivative, abutadiene compound, a polystyrene derivative, a triphenylmethanederivative, and a tetraphenylbenzene derivative, and a combinationthereof. The hole transporting material 12M may further contain, in amolecular structure thereof, a group such as a soluble group, across-linking group, and a thermal dissociation soluble group, forexample, for functions of solubility and insolubilization.

The organic light-emitting layer 13 may serve to emit light of apredetermined color by recombination of holes and electrons. The organiclight-emitting layer 13 may be a coated film, and may be formed, forexample, by coating and drying of a solution containing the organiclight-emitting material 13M as a solute. The solution having the organiclight-emitting material 13M as a solute may include, for example, theorganic light-emitting material 13M and a solvent. The organiclight-emitting layer 13 may be a layer that emits light throughgeneration of excitons caused by recombination, inside the organiclight-emitting layer 13, of holes injected from the anode 11 andelectrons injected from the cathode 15. The organic light-emitting layer13 may be, for example, a blue light-emitting layer made of a blueorganic light-emitting material. The organic light-emitting material 13Mthat is a raw material, i.e., a material of the organic light-emittinglayer 13 may be, for example, a single dopant material, but morepreferably may be a combination of a host material and the dopantmaterial. In other words, the organic light-emitting layer 13 mayinclude, as the organic light-emitting material, the host material andthe dopant material. The host material serves a main function oftransporting charge of electrons or holes, and the dopant materialserves a light-emitting function. Each of the host material and thedopant material is not only limited to a single type material, but mayalso be a combination of two or more types of materials. The amount ofthe dopant material to the host material may be preferably in a rangefrom 0.01% by weight to 30% by weight, and more preferably from 0.01% byweight to 10% by weight.

Examples of the host material of the organic light-emitting layer 13 mayinclude an amine compound, a condensed polycyclic aromatic compound, anda heterocyclic compound. Examples of the amine compound may include amonoamine derivative, a diamine derivative, a triamine derivative, and atetraamine derivative. Example of the condensed polycyclic aromaticcompound may include an anthracene derivative, a naphthalene derivative,a naphthacene derivative, a phenanthrene derivative, a chrysenederivative, a fluoranthene derivative, a triphenylene derivative, apentacene derivative, and a perylene derivative. Example of theheterocyclic compound may include a carbazole derivative, a furanderivative, a pyridine derivative, a pyrimidine derivative, a triazinederivative, an imidazole derivative, a pyrazole derivative, a triazolederivative, an oxazole derivative, an oxadiazole derivative, a pyrrolederivative, an indole derivative, an azaindole derivative, anazacarbazole derivative, a pyrazoline derivative, a pyrazolonederivative, and a phthalocyanine derivative.

Examples of the dopant material of the organic light-emitting layer 13may include a pyrene derivative, a fluoranthene derivative, anarylacetylene derivative, a fluorene derivative, a perylene derivative,an oxadiazole derivative, an anthracene derivative, and a chrysenederivative. In addition, a metal complex may also be used for the dopantmaterial of the organic light-emitting layer 13. Examples of the metalcomplex may include a metal complex containing a ligand and an atom ofmetal such as iridium (Ir), platinum (Pt), osmium (Os), gold (Au),rhenium (Re), and ruthenium (Ru).

The organic light-emitting layer 13 may be made of an organiclight-emitting material having hole mobility that is larger thanelectron mobility. In other words, the organic light-emitting layer 13may be a layer made of a material having a higher hole transportingproperty, and may be a layer having hole mobility that is larger thanelectron mobility. A constituent material of each of the hole transportlayer 12 and the electron transport layer 14 may be a material inaccordance with the constituent material of the organic light-emittinglayer 13.

The electron transport layer 14 may serve to transport electronsinjected from the cathode 15 to the organic light-emitting layer 13. Theelectron transport layer 14 may be a deposited film. The electrontransport layer 14 may be made of, for example, an organic materialhaving an electron transporting property (hereinafter, referred to as“electron transporting material 14M”). The electron transport layer 14may be made of an organic material having a hole-blocking property aswell as a wide energy gap suitable for preventing exciton deactivation.The electron transport layer 14 may be made of an organic materialhaving an energy gap which is larger than an energy gap in the organiclight-emitting layer 13.

The electron transport layer 14 may be interposed between the organiclight-emitting layer 13 and the cathode 15, and may serve to transportelectrons injected from the cathode 15 to the organic light-emittinglayer 13. It is to be noted that the electron transport layer 14 maypreferably further have functions such as a charge-blocking function ofsuppressing tunneling of charges (i.e., holes in the present embodiment)to the cathode 15 from the organic light-emitting layer 13, and afunction of suppressing light extinction in an excitation state of theorganic light-emitting layer 13. The electron transporting material 14Mthat is a raw material, i.e., a material of the electron transport layer14 may be, for example, an aromatic heterocyclic compound containing oneor more hetero atoms in a molecule. Examples of the aromaticheterocyclic compound may include a compound containing, as a skeleton,a pyridine ring, a pyrimidine ring, a triazine ring, a benzimidazolering, a phenanthroline ring, and a quinazoline ring. The electrontransport layer 14 may also contain metal having the electrontransporting property. The electron transport layer 14 that contains themetal having the electron transporting property may enhance the electrontransporting property of the electron transport layer 14. Examples ofthe metal contained in the electron transport layer 14 may includebarium (Ba), lithium (Li), calcium (Ca), potassium (K), cesium (Cs),sodium (Na), and rubidium (Rb).

The cathode 15 may be a reflective electrode having light reflectivity,and may be, for example, a metal electrode made of a metal materialhaving reflectivity. Examples of the material of the cathode 15 mayinclude aluminum (Al), magnesium (Mg), silver (Ag), an aluminum-lithiumalloy, and a magnesium-silver alloy. It is to be noted that the cathode15 is not only limited to the reflective electrode, but may also be atransparent electrode made of an ITO film, for example, as with theanode 11. In the present embodiment, the substrate 10 and the anode 11may each have translucency, and the cathode 15 has reflectivity. Thus,the organic electroluminescence device 1 has a bottom emission structurein which light is emitted from the substrate 10. It is to be noted thatthe organic electroluminescence device 1 is not only limited to havingthe bottom emission structure, but may also have a top emissionstructure.

Description is next given of an example feature of the organicelectroluminescence device 1 according to the present embodiment alsowith reference to comparative examples. (A) of FIG. 2 schematicallyillustrates an example of energy band structures of respective layers ofthe organic electroluminescence device 1. (B) of FIG. 2 illustrates anexample of absorption spectra of the hole transport layer 12 and theelectron transport layer 14 in (A) of FIG. 2 as well as an example of anemission spectrum of the organic light-emitting layer 13 in (A) of FIG.2. (A) of FIG. 3 schematically illustrates an example of energy bandstructures of respective layers of an organic electroluminescence deviceof Comparative Example A. (B) of FIG. 3 illustrates an example ofabsorption spectra of a hole transport layer 112 and an electrontransport layer 114 in (A) of FIG. 3 as well as an example of anemission spectrum of an organic light-emitting layer 113 in (A) of FIG.3. (A) of FIG. 4 schematically illustrates an example of energy bandstructures of respective layers of an organic electroluminescence deviceaccording to Comparative Example B. (B) of FIG. 4 illustrates an exampleof absorption spectra of the hole transport layer 12 and the electrontransport layer 14 in (A) of FIG. 4 as well as an example of an emissionspectrum of an organic light-emitting layer 213 in (A) of FIG. 4.

In each (A) of FIGS. 2, 3, and 4, the upper line indicates the lowestunoccupied molecular orbital (LUMO), and the lower line indicates thehighest occupied molecular orbital (HOMO). The energy gap is an energydifference between HOMO level and LUMO level. The energy gap is alsoreferred to as a band gap. When the organic light-emitting layercontains the dopant material, in particular, when the organiclight-emitting layer contains two or more dopant materials, the energygap of the organic light-emitting layer indicates an energy gap of adopant material having the narrowest energy gap.

[Method for Measuring HOMO Level and LUMO Level]

Examples of the method for measuring the HOMO level may includeatmospheric photoelectron spectroscopy, an electrochemical method suchas cyclic voltammetry, and photoelectron spectroscopy (PES). Incontrast, examples of the method for measuring the LUMO level mayinclude inverse photoelectron spectroscopy (IPES) and a method ofcalculation from the HOMO level and an energy gap determined from anabsorption end by means of photoabsorption spectroscopy. Alternatively,a calculation by molecular orbital method may also be used to calculatethe HOMO level and the LUMO level.

The organic electroluminescence device of Comparative Example A may havea structure of a deposited organic electroluminescence device in whichthe hole transport layer 112 as a deposited film, the organiclight-emitting layer 113 as a deposited film, and the electron transportlayer 14 as a deposited film are stacked in this order. The organicelectroluminescence device of Comparative Example B may have a structureof a coated organic electroluminescence device in which the holetransport layer 12 as a coated film, the organic light-emitting layer213 as a coated film, and the electron transport layer 14 as a depositedfilm are stacked in this order.

The hole transport layer 112 may be an organic material layer configuredby a deposited film. Examples of the material of the hole transportlayer 112 may include an arylamine derivative, a triazole derivative, anoxadiazole derivative, an imidazole derivative, a polyarylalkanederivative, a pyrazoline derivative and a pyrazolone derivative, aphenylenediamine derivative, an amino-substituted chalcone derivative,an oxazole derivative, a styrylanthracene derivative, a fluorenonederivative, a hydrazone derivative, a stilbene derivative, a butadienecompound, a polystyrene derivative, a triphenylmethane derivative, and atetraphenylbenzene derivative. An energy gap Eg4 in the hole transportlayer 112 may be wider than an energy gap Eg5 in the organiclight-emitting layer 113.

The organic light-emitting layer 113 may be a blue organiclight-emitting material layer configured by a deposited film using ablue organic light-emitting material different from that of the organiclight-emitting layer 13. The material of the organic light-emittinglayer 113 may be a single dopant material, but more preferably acombination of the host material and the dopant material. The hostmaterial serves a main function of transporting charge of electrons orholes, and the dopant material serves a light-emitting function. Thehost material contained in the organic light-emitting layer 113 is notonly limited to a single type material, but may also be a combination oftwo or more types of materials. The amount of the dopant materialcontained in the organic light-emitting layer 113, relative to the hostmaterial contained in the organic light-emitting layer 113, may bepreferably in a range from 0.01% by weight to 30% by weight, and morepreferably from 0.01% by weight to 10% by weight.

Examples of the host material of the organic light-emitting layer 113may include an amine compound, a condensed polycyclic aromatic compound,and a heterocyclic compound. Examples of the amine compound may includea monoamine derivative, a diamine derivative, a triamine derivative, anda tetraamine derivative. Example of the condensed polycyclic aromaticcompound may include an anthracene derivative, a naphthalene derivative,a naphthacene derivative, a phenanthrene derivative, a chrysenederivative, a fluoranthene derivative, a triphenylene derivative, apentacene derivative, and a perylene derivative. Example of theheterocyclic compound may include a carbazole derivative, a furanderivative, a pyridine derivative, a pyrimidine derivative, a triazinederivative, an imidazole derivative, a pyrazole derivative, a triazolederivative, an oxazole derivative, an oxadiazole derivative, a pyrrolederivative, an indole derivative, an azaindole derivative, anazacarbazole derivative, a pyrazoline derivative, a pyrazolonederivative, and a phthalocyanine derivative.

Examples of the dopant material of the organic light-emitting layer 113may include a pyrene derivative, a fluoranthene derivative, anarylacetylene derivative, a fluorene derivative, a perylene derivative,an oxadiazole derivative, an anthracene derivative, and a chrysenederivative. In addition, a metal complex may also be used for the dopantmaterial of the organic light-emitting layer 113. Examples of the metalcomplex may include a metal complex containing a ligand and an atom ofmetal such as iridium (Ir), platinum (Pt), osmium (Os), gold (Au),rhenium (Re), and ruthenium (Ru).

The energy gap Eg5 in the organic light-emitting layer 113 may besubstantially equal to an energy gap Eg2 in the organic light-emittinglayer 13. Accordingly, an emission wavelength of the organiclight-emitting layer 113 may be substantially equal to an emissionwavelength of the organic light-emitting layer 13.

The organic light-emitting layer 213 may be a blue organiclight-emitting layer configured by a coated film using a blue organiclight-emitting material different from those of the organiclight-emitting layer 13 and the organic light-emitting layer 113.Examples of the material of the organic light-emitting layer 213 mayinclude a polymeric blue light-emitting material such as polyfluoreneand a derivative thereof, polyphenylene and a derivative thereof, andpolyarylamine and a derivative thereof. An energy gap in the organiclight-emitting layer 213 may be substantially equal to the energy gap inthe organic light-emitting layer 13. Accordingly, an emission wavelengthof the organic light-emitting layer 213 may be substantially equal tothe emission wavelength of the organic light-emitting layer 13.

As described above, the hole transport layer 12 may be configured by thecoated film, and may be a hole transport layer insolubilized with theinsoluble function. Therefore, an energy gap Eg1 in the hole transportlayer 12 may be narrower than the energy gap Eg4 in the hole transportlayer 112. As a result, the energy gap Eg1 in the hole transport layer12 may not be an energy gap sufficiently larger than the energy gap Eg2in the organic light-emitting layer 13, and, for example, may besubstantially equal to the energy gap Eg2 in the organic light-emittinglayer 13.

As described above, the organic light-emitting layer 13 may be adeposited film, and may be made of an organic light-emitting materialhaving hole mobility that is larger than electron mobility. In otherwords, the organic light-emitting layer 13 may be a layer made of amaterial having a higher hole transporting property, and may also be alayer having hole mobility that is larger than electron mobility.Consequently, a light emission region 13A in the organic light-emittinglayer 13 may be positioned in a region on electron-injection side, i.e.,electron transport layer 14 side inside the organic light-emitting layer13. In other words, the light emission region 13A in the organiclight-emitting layer 13 may be positioned in a region distant from aregion on hole-injection side, i.e., hole transport layer 12 side insidethe organic light-emitting layer 13. That is, the organic light-emittinglayer 13 may have the light emission region 13A on electron transportlayer 14 side inside the organic light-emitting layer 13. The lightemission region 13A may be preferably positioned in a region of theorganic light-emitting layer 13 in the vicinity of an interface withrespect to the electron transport layer 14. As a result, deactivationdue to the hole transport layer 12 is less likely to occur despite afact that at least a portion of an emission spectrum 13 a in the organiclight-emitting layer 13 overlaps an absorption spectrum 12 a in the holetransport layer 12.

As described above, the electron transport layer 14 may be configured bya deposited film. Thus, it is possible to easily select, as the materialof the electron transport layer 14, a material having an energy gap Eg3that is wider than the energy gap Eg2 in the organic light-emittinglayer 13. In other words, the energy gap Eg3 of the electron transportlayer 14 is larger than the energy gap Eg2 of the organic light-emittinglayer 13. Consequently, deactivation due to the electron transport layer14 is less likely to occur because the emission spectrum 13 a in theorganic light-emitting layer 13 does not overlap an absorption spectrum14 a in the electron transport layer 14.

As described above, in Comparative Example B, the organic light-emittinglayer 213 may be a polymeric blue organic light-emitting material layerconfigured by a coated film of the polymeric blue organic light-emittingmaterial. Further, an energy gap Eg6 in the organic light-emitting layer213 may be substantially equal to the energy gap Eg2 in the organiclight-emitting layer 13. At this time, the deactivation due to the holetransport layer 12 may occur because at least a portion of an emissionspectrum 213 a in the organic light-emitting layer 213 overlaps theabsorption spectrum 12 a in the hole transport layer 12.

In Comparative Example A, deactivation due to the hole transport layer112 is less likely to occur in the first place, because an emissionspectrum 113 a in the organic light-emitting layer 113 does not overlapan absorption spectrum 112 a in the hole transport layer 112. InComparative Example A, however, the hole transport layer 112 and theorganic light-emitting layer 113 may be each configured by the depositedfilm, thus resulting in disadvantages such as high cost, a complicatedmanufacturing process, and difficulty in forming the layers at a largearea scale, compared to the organic electroluminescence device ofComparative Example B and the organic electroluminescence device 1 ofthe present embodiment.

Description is next given of a light emission region of each of theorganic light-emitting layers. The light emission region indicates adistribution of excitons, which are generated in the organiclight-emitting layer, inside the organic light-emitting layer. FIGS. 5Ato 5D each illustrate an example of the light emission region inside theorganic light-emitting layer. In each of FIGS. 5A to 5D, the organiclight-emitting layer is separated at the middle to be divided into tworegions, i.e., a region on side where the hole transport layer isdisposed and a region on side where the electron transport layer isdisposed. As used herein, the wording “the light emission region lies onelectron transport layer side” refers to, for example, a state in which50% or more of the light emission region inside the organiclight-emitting layer exists in the region on side where the electrontransport layer is disposed, as illustrated in FIG. 5A. As used herein,the wording “the light emission region lies on hole transport layerside” refers to, for example, a state in which 50% or more of the lightemission region inside the organic light-emitting layer exists in theregion on side where the hole transport layer is disposed, asillustrated in FIG. 5B. As used herein, the wording “the light emissionregion is positioned in the vicinity of an interface with respect to theelectron transport layer” refers to, for example, a state in which 90%or more of the light emission region inside the organic light-emittinglayer exists on side where the electron transport layer is disposed, asillustrated in FIG. 5C. As used herein, the wording “the light emissionregion is positioned in the vicinity of an interface with respect to thehole transport layer” refers to, for example, a state in which 90% ormore of the light emission region inside the organic light-emittinglayer exists in the region on side where the hole transport layer isdisposed, as illustrated in FIG. 5D. It is to be noted that FIGS. 5A to5D each illustrate an example of the light emission region. For example,there is also a case where a peak of the light emission region ispositioned inside the organic light-emitting layer instead of beingpositioned at the interface of the organic light-emitting layer.

In order to achieve a superior device performance even in the case ofthe coated organic electroluminescence device, the inventors focusedattention on the light emission region inside the organic light-emittinglayer to evaluate the device performance of the organicelectroluminescence device. More specifically, evaluation was made foreach light emission efficiency of a case where the light emission region13A is set on electron transport layer 14 side of the organiclight-emitting layer 13 and of a case where the light emission region13A is set on hole transport layer 12 side of the organic light-emittinglayer 13, in the organic electroluminescence device 1 of FIG. 1.Description is given below of experiments and evaluation results of thedevice performance. It is to be noted that the disclosure is not limitedto the contents described in the examples.

Example 1

[Organic Electroluminescence Device in which Light Emission Region 13ALies on Electron Transport Layer 14 Side]

As the organic electroluminescence device of Example 1, a hole injectionlayer, a hole transport layer, an organic light-emitting layer, anelectron transport layer, an electron injection layer, and aluminum werestacked in this order on a glass substrate on which an ITO transparentelectrode was patterned. The organic light-emitting layer was set tohave a film thickness of 40 nm to 50 nm.

Comparative Example 1

[Organic Electroluminescence Device in which Light Emission Region Lieson Hole Transport Layer Side]

An organic electroluminescence device of Comparative Example 1 wasprepared, in which a patterned ITO transparent electrode, a holeinjection layer, a hole transport layer, an organic light-emittinglayer, an electron transport layer, an electron injection layer, andaluminum were stacked in this order on a glass substrate. The organiclight-emitting layer was set to have a film thickness of 40 nm to 50 nm.The organic light-emitting layer of Comparative Example 1 is a coatedfilm, and is made of an organic light-emitting material having holemobility that is smaller than electron mobility. In other words, theorganic light-emitting layer of Comparative Example 1 is a layer made ofa material having a higher electron transporting property, and is alayer having hole mobility that is smaller than electron mobility. InComparative Example 1, a constituent material of each of the holeinjection layer, the hole transport layer, the electron transport layer,and the electron injection layer is a material in accordance with theconstituent material of the organic light-emitting layer of ComparativeExample 1. In contrast, the organic light-emitting layer of Example 1 isa coated film, and may be made of an organic light-emitting materialhaving hole mobility that is larger than electron mobility. In otherwords, the organic light-emitting layer of Example 1 may be a layer madeof a material having a higher hole transporting property, and may be alayer having hole mobility that is larger than electron mobility. InExample 1, a constituent material of each of the hole injection layer,the hole transport layer, the electron transport layer, and the electroninjection layer may be a material in accordance with the constituentmaterial of the organic light-emitting layer of Example 1. Accordingly,the organic electroluminescence device of Example 1 has the lightemission region that is positioned on electron transport layer side,whereas the organic electroluminescence device of Comparative Example 1has the light emission region that is positioned on hole transport layerside. The method for varying the light emission region may be, forexample, a method in which a ratio between the host material and thedopant material contained in the organic light-emitting layer isadjusted to allow the hole mobility to be larger than the electronmobility in the organic light-emitting layer.

Description is given of a method for evaluating the light emissionregion inside the organic light-emitting layer of each of the organicelectroluminescence devices fabricated in Example 1 and ComparativeExample 1.

In the present experiment, viewing angle characteristics of the organicelectroluminescence device were evaluated to analyze the light emissionregion inside the organic light-emitting layer. Table 1 belowillustrates variations) Δy(30°)=y(0°)−y(30°) and Δy(60°)=y(0°)−y(60°)which are respective variations of light emission chromaticity y(30°)and y(60°) from front chromaticity y(0°) measured respectively indirections of 30° and 60° when a direction perpendicular to thesubstrate of the organic electroluminescence device is set at 0° (i.e.,a frontal direction to an emission surface). The measurement wasperformed using a spectral radiance meter.

[Actual Measurement of Variation of Chromaticity y from FrontChromaticity]

TABLE 1 Δy (30°) Δy (60°) Example 1 −0.013 −0.020 Comparative Example 1−0.024 −0.052

Next, optical calculation of viewing angle characteristics was performedusing optical simulation for each device structure of the organicelectroluminescence devices of Example 1 and Comparative Example 1.Examples of the light emission region inside the organic light-emittinglayer may include a Gaussian distribution and an exponentialdistribution. The Gaussian distribution is a distribution represented byExpression (1). The exponential distribution is a distributionrepresented by Expression (2).

Exp.(−(a−a0)²/2σ²)  Expression (1)

In Expression (1), “a” denotes a position inside the organiclight-emitting layer, a0 denotes a peak position of the light emissionregion inside the organic light-emitting layer, and σ denotes ahalf-value width.

Exp.(−|b−b0|/w)  Expression (2)

In Expression (2), “b” denotes a position inside the organiclight-emitting layer, b0 denotes a peak position of the light emissionregion inside the organic light-emitting layer, and w denotes a constantthat specifies the width of the light emission region.

[Calculation 1 in a Case where Light Emission Region Lies on ElectronTransport Layer Side]

(Optical Calculation 1)

Calculation was performed using the Gaussian distribution of Expression(1) for a model in which the peak of the light emission region ispositioned on side, of the organic light-emitting layer, where theelectron transport layer is disposed. The position “a” was set at such aposition as to allow the ratio of a distance from an interface betweenthe organic light-emitting layer and the hole transport layer to adistance from an interface between the organic light-emitting layer andthe electron transport layer to be 8:2. The half-value width σ was setat 5 nm.

[Calculation 2 in a Case where Light Emission Region Lies on ElectronTransport Layer Side]

(Optical Calculation 2)

Calculation was performed using the exponential distribution ofExpression (2) for a model in which the peak of the light emissionregion is positioned at an interface between the organic light-emittinglayer and the electron transport layer. The position “b” was set at theinterface between the organic light-emitting layer and the electrontransport layer. The constant w was set at 5 nm.

[Calculation 3 in a Case where Light Emission Region Lies on HoleTransport Layer Side]

(Optical Calculation 3)

Calculation was performed using the Gaussian distribution of Expression(1) for a model in which the peak of the light emission region ispositioned on side, of the organic light-emitting layer, where the holetransport layer is disposed. The position “a” was set at such a positionas to allow the ratio of a distance from the interface between theorganic light-emitting layer and the hole transport layer to a distancefrom the interface between the organic light-emitting layer and theelectron transport layer to be 2:8. The half-value width σ was set at 5nm.

[Calculation 4 in a Case where Light Emission Region Lies on HoleTransport Layer Side]

(Optical Calculation 4)

Calculation was performed using the exponential distribution ofExpression (2) for a model in which the peak of the light emissionregion is positioned at an interface between the organic light-emittinglayer and the hole transport layer. The position “b” was set at theinterface between the organic light-emitting layer and the holetransport layer. The constant w was set at 5 nm.

Table 2 below illustrates calculation results of Optical Calculations 1,2, 3, and 4. It is appreciated, from Tables 1 and 2, that opticalsimulation results coincide well with experimental results. Example 1well coincides with Optical Calculation 2, in particular, among OpticalCalculations 1 and 2 in cases where the light emission region lies onelectron transport layer side. Further, Comparative Example 1 wellcoincides with Optical Calculation 4, in particular, among OpticalCalculations 3 and 4 in cases where the light emission region lies onhole transport layer side. Accordingly, Example 1 that well coincideswith Optical Calculation 2 in the case of having the light emissionregion on electron transport layer side demonstrates that the lightemission region inside the organic light-emitting layer lies on electrontransport layer side. Further, Comparative Example 1 that well coincideswith Optical Calculation 4 in the case of having the light emissionregion on hole transport layer side demonstrates that the light emissionregion inside the organic light-emitting layer lies on hole transportlayer side.

Moreover, the organic light-emitting layer in Example 1 may have a filmthickness of 40 nm to 50 nm. Therefore, it is appreciated that 90% ormore of the light emission region in Optical Calculation 2 exists onside, of the organic light-emitting layer, where the electron transportlayer is disposed, and thus the light emission region in OpticalCalculation 2 lies in the vicinity of the electron transport layer.Further, the organic light-emitting layer in Comparative Example 1 has afilm thickness of 40 nm to 50 nm. Therefore, it is appreciated that 90%or more of the light emission region in Optical Calculation 4 exists onside, of the organic light-emitting layer, where the hole transportlayer is disposed, and thus the light emission region in OpticalCalculation 4 lies in the vicinity of the hole transport layer.

[Variation of Chromaticity y from Front Chromaticity Calculated byOptical Simulation]

TABLE 2 Δy (30°) Δy (60°) Optical Calculation 1 −0.013 −0.023 OpticalCalculation 2 −0.012 −0.021 Optical Calculation 3 −0.025 −0.057 OpticalCalculation 4 −0.024 −0.053

Table 3 below illustrates an example of each light emission efficiencyof the organic electroluminescence devices of Example 1 and ComparativeExample 1. The light emission efficiency of Example 1 of Table 3 is astandardized value of the experimental value of the light emissionefficiency of Example 1 with the experimental value of the lightemission efficiency of Comparative Example 1. The light emissionefficiency of Comparative Example 1 of Table 3 is a standardized valueof the experimental value of the light emission efficiency ofComparative Example 1 with the experimental value of the light emissionefficiency of Comparative Example 1. It is appreciated, from Table 3,that the light emission efficiency is increased by about two times byshifting the light emission region from hole transport layer side toelectron transport layer side.

[Comparison of Light Emission Efficiency (EQE)]

TABLE 3 Light Emission Efficiency Example 1 2.19 Comparative Example 11.00

As a result of intensive study on the basis of the above-describedexperimental results and evaluations, the inventors have obtained thefollowing knowledge. That is, by allowing the light emission regioninside the organic light-emitting layer to be positioned on electrontransport layer side, more preferably in the vicinity of an interfacewith respect to the electron transport layer, it becomes possible tosuppress movement of energy from the organic light-emitting layer to thehole transport layer, and to suppress light extinction that occursbetween the organic light-emitting layer and the hole transport layer,thus improving the light emission efficiency in the coated organicelectroluminescence device.

[Other Features]

Description is given of other example features in the organicelectroluminescence device 1 of the present embodiment.

(Feature 1)

Evaluation was made of a hole current and an electron current in theorganic light-emitting layer 13 in the present embodiment. The holecurrent is generated by flow of holes, and the electron current isgenerated by flow of electrons. However, it is difficult to separate thehole current from the electron current in the organicelectroluminescence device in which holes and electrons flow at the sametime. Therefore, a single charge device was fabricated for evaluation. Ahole only device (HOD) was fabricated to evaluate the hole current. TheHOD of Example 1 and the HOD of Comparative Example 1 each have a devicestructure made of gold changed from aluminum, in which the organiclight-emitting layer of the organic electroluminescence device of eachof Example 1 and Comparative Example 1 is set to have a film thicknessof 75 nm to 85 nm, and the electron transport layer and the electroninjection layer are removed. A hole current Ih is defined as a currentvalue in the case where a predetermined voltage is applied to the HODthat allows only holes to flow. An electron only device (EOD) wasfabricated to evaluate the electron current. The EOD of Example 1 andthe EOD of Comparative Example 1 each have a device structure, in whichthe organic light-emitting layer of the organic electroluminescencedevice of each of Example 1 and Comparative Example 1 is set to have afilm thickness of 75 nm to 85 nm, and the hole injection layer and thehole transport layer are removed. An electron current Ie is defined as acurrent value in the case where a predetermined voltage is applied tothe EOD that allows only electrons to flow.

Table 4 below illustrates an example of a current density (unit: mA/cm²)of the HOD and the EOD of each of Example 1 and Comparative Example 1,and an example of evaluation of a quotient of the hole current Ihdivided by the electron current Ie, in a case where a voltage of 5 V isapplied to the HOD and the EOD of each of Example 1 and ComparativeExample 1. The upper row in Table 4 illustrates the current density ofthe HOD and the EOD of Example 1 as well as the quotient of the holecurrent Ih divided by the electron current Ie. The lower row in Table 4illustrates the current density of the HOD and the EOD of ComparativeExample 1 as well as the quotient of the hole current Ih divided by theelectron current Ie. It is appreciated, from Table 4, that the HOD ofExample 1 has a current density that is larger than a current density ofthe EOD of Example 1, and that the quotient of the hole current Ihdivided by the electron current Ie is larger than one. It is alsoappreciated, from Table 4, that the HOD of Comparative Example 1 has acurrent density that is smaller than a current density of the EOD ofComparative Example 1, and that the quotient of the hole current Ihdivided by the electron current Ie is smaller than one. Accordingly, itmay be presumed that, in Example 1, the hole current in the organiclight-emitting layer is larger than the electron current in the organiclight-emitting layer, thus allowing the light emission region to lie onelectron transport layer side. Further, it may be said, in Example 1,that the organic light-emitting layer is configured to allow theposition of the light emission region inside the organic light-emittinglayer to come closer to the electron transport layer, as the quotient ofthe hole current Ih divided by the electron current Ie becomes larger.Furthermore, it may be presumed that, in Comparative Example 1, thelight emission region lies on hole transport layer side because the holecurrent is smaller than the electron current. These views support thepresumption that the light emission region of Example 1 lies on electrontransport layer side, and that the light emission region of ComparativeExample 1 lies on hole transport layer side. Accordingly, the coatedorganic electroluminescence device may preferably have a configurationin which the hole current Ih in the organic light-emitting layer islarger than the electron current Ie in the organic light-emitting layer,i.e., the quotient of the hole current Ih divided by the electroncurrent Ie is larger than one.

TABLE 4 Current Current Density of Density of HOD EOD 1h/1e Example 12.0 0.3 6.7 Comparative 1.9 7.0 0.3 Example 1

(Feature 2)

Evaluation was made of the hole mobility and the electron mobility inthe organic light-emitting layer 13 in the present embodiment. Examplesof the method for evaluating the mobility may include a method ofdetermining the mobility from current-voltage characteristics of aspace-charge limited current, an evaluation method using atime-of-flight method in which a predetermined device is irradiated withpulse light to determine the mobility from a time during which a carriertravels between electrodes, and an evaluation method using impedancespectroscopy in which the mobility is determined from a transit-timeeffect in the case of applying an alternating voltage to the organicelectroluminescence device. It is difficult to separate the holemobility from the electron mobility in the organic electroluminescencedevice in which holes and electrons flow at the same time. Therefore, asingle charge device was fabricated for evaluation. The HOD wasfabricated to evaluate the hole mobility. The HOD of Example 1 and theHOD of Comparative Example 1 each have a device structure made of goldchanged from aluminum, in which the organic light-emitting layer of theorganic electroluminescence device of each of Example 1 and ComparativeExample 1 is set to have a film thickness of 75 nm to 85 nm, and theelectron transport layer and the electron injection layer are removed.Hole mobility μh is defined as mobility in the case where apredetermined voltage is applied to the HOD that allows only holes toflow. The EOD was fabricated to evaluate the electron mobility. The EODof Example 1 and the EOD of Comparative Example 1 each have a devicestructure, in which the organic light-emitting layer of the organicelectroluminescence device of each of Example 1 and Comparative Example1 is set to have a film thickness of 75 nm to 85 nm, and the holeinjection layer and the hole transport layer are removed. Electronmobility μe is defined as mobility in the case where a predeterminedvoltage is applied to the EOD that allows only electrons to flow.

Table 5 below illustrates an example of mobility in the organiclight-emitting layer of the HOD and the EOD of each of Example 1 andComparative Example 1, and an example of evaluation of a quotient of thehole mobility μh divided by the electron mobility μe, in a case where avoltage of 5 V is applied to the HOD and the EOD of each of Example 1and Comparative Example 1. The upper row in Table 5 illustrates themobility in the organic light-emitting layer of the HOD and the EOD ofExample 1 as well as the quotient of the hole mobility μh divided by theelectron mobility μe. The lower row in Table 5 illustrates the mobilityin the organic light-emitting layer of the HOD and the EOD ofComparative Example 1 as well as the quotient of the hole mobility μhdivided by the electron mobility μe. It is appreciated, from Table 5,that the hole mobility in the organic light-emitting layer of the HOD ofExample 1 is larger than the electron mobility in the organiclight-emitting layer of the EOD of Example 1, and that the quotient ofthe hole mobility μh divided by the electron mobility μe is larger thanone. It is also appreciated, from Table 5, that the hole mobility in theorganic light-emitting layer of the HOD of Comparative Example 1 issmaller than the electron mobility in the organic light-emitting layerof the EOD of Comparative Example 1, and that the quotient of the holemobility μh divided by the electron mobility μe is smaller than one.Accordingly, it may be presumed that, in Example 1, the hole mobility islarger than the electron mobility, thus allowing the light emissionregion to lie on electron transport layer side. Further, it may bepresumed that, in Comparative Example 1, the light emission region lieson hole transport layer side because the hole mobility is smaller thanthe electron mobility. These views support the presumption that thelight emission region of Example 1 lies on electron transport layerside, and that the light emission region of Comparative Example 1 lieson hole transport layer side. Accordingly, the coated organicelectroluminescence device may preferably have a configuration in whichthe hole mobility μh is larger than the electron mobility μe, i.e., thequotient of the hole mobility μh divided by the electron mobility μe islarger than one.

TABLE 5 Mobility Mobility in HOD in EOD μh/μe Example 1 1.3E−10 9.3E−1214.4 Comparative 2.1E−10 3.7E−10 0.6 Example 1

(Feature 3)

Evaluation was made of a molecular orientation degree of the organiclight-emitting material in the organic light-emitting layer 13 in thepresent embodiment. Examples of the method for evaluating the molecularorientation degree may include analysis of optical anisotropy usingspectroscopic ellipsometry. The evaluation of the molecular orientationdegree was made of a single film of the organic light-emitting layerformed on quartz glass. As a parameter indicating the molecularorientation degree, a parameter S represented by Expression (3) and aparameter S′ represented by Expression (4) may be used.

S=(ke−ko)/(ke+2×ko)  Expression (3)

S′=(2×ko)/(ke+2×ko)  Expression (4)

In Expression (3) and Expression (4), ko denotes an extinctioncoefficient in a film-plane direction of the organic light-emittinglayer in an emission wavelength, and ke denotes an extinctioncoefficient in a film-thickness direction of the organic light-emittinglayer in an emission wavelength. Here, for example, the parameter Sranges from −1 to 0.5 (−1≦S≦0.5). When S is equal to −1 (S=−1), themolecular orientation is completely horizontal relative to thesubstrate. When S is equal to 0.5 (S=0.5), the molecular orientation iscompletely vertical relative to the substrate. When S is equal to 0(S=0), the molecular orientation is completely disorderly, i.e., random.Likewise, the parameter S′ ranges from 0 to 1 (0≦S′≦1). When S′ is equalto 1 (S′=1), the molecular orientation is completely horizontal relativeto the substrate. When S′ is equal to 0 (S′=0), the molecularorientation is completely vertical relative to the substrate. When S′ isequal to 0.66 . . . , i.e., ⅔ (S′=⅔), the molecular orientation iscompletely disorderly, i.e., random.

Table 6 below illustrates an example of a case of evaluating theparameter S′ indicating the molecular orientation degree of the organiclight-emitting layer of each of Example 1 and Comparative Example 1formed on a quartz substrate. The upper row of Table 6 illustrates avalue of the parameter S′ indicating the molecular orientation degree ofthe organic light-emitting layer of Example 1, and the lower row ofTable 6 illustrates a value of the parameter S′ indicating the molecularorientation degree of the organic light-emitting layer of ComparativeExample 1. It is appreciated, from Table 6, that the value 0.675 of theparameter S′ of the organic light-emitting layer of Example 1 is veryclose to 0.66 . . . , i.e., ⅔, and thus the molecular orientation of theorganic light-emitting layer of Example 1 is disorderly, i.e., random.It is also appreciated, from Table 6, that the value of the parameter S′of the organic light-emitting layer of Comparative Example 1 is 0.749,and thus the molecular orientation of the organic light-emitting layerof Comparative Example 1 is more horizontal relative to the substratethan the molecular orientation of the organic light-emitting layer ofExample 1. Accordingly, the molecular orientation of the organiclight-emitting layer is disorderly, i.e., random in Example 1, whereas,in Comparative Example 1, the molecular orientation of the organiclight-emitting layer is more horizontal relative to the substrate thanthat of Example 1. It is presumed that the light emission region ischanged due to such a difference in the molecular orientation degree,i.e., the light emission region is changed by changing a film property.The change in the film property may be generated by difference in thematerial of the organic light-emitting layer. Accordingly, it ispresumed that the disorderly, i.e., random molecular orientation of theorganic light-emitting layer in Example 1 causes the light emissionregion to be shifted to electron transport layer side. It is alsopresumed that the molecular orientation of the organic light-emittinglayer relative to the substrate in Comparative Example 1 is morehorizontal than the molecular orientation of the organic light-emittinglayer of Example 1, which causes the light emission region to be shiftedto hole transport layer side. Accordingly, in the coated organicelectroluminescence device, it is preferable for the parameter S′indicating the molecular orientation degree to be larger than 0.66 andto be smaller than 0.75 (0.66<S′<0.75). In this case, the direction ofthe molecular orientation of the organic light-emitting material in theorganic light-emitting layer of Example 1 may be determined to allow theratio of x (or y):z to range from 1:1 to 1.5:1, where the x-axis and they-axis are defined as directions orthogonal to each other in thefilm-plane direction of the organic light-emitting layer, and the z-axisis defined as the film-thickness direction of the organic light-emittinglayer. More preferably, the parameter S′ indicating the molecularorientation degree may be larger than 0.66 and smaller than 0.72(0.66<S′<0.72). In this case, the direction of the molecular orientationof the organic light-emitting material in the organic light-emittinglayer of Example 1 may be determined to allow the ratio of x (or y):z torange from 1:1 to 1.29:1. Still more preferably, the parameter S′ may belarger than 0.66 and smaller than 0.69 (0.66<S′<0.69). In this case, thedirection of the molecular orientation of the organic light-emittingmaterial in the organic light-emitting layer of Example 1 may bedetermined to allow the ratio of x (or y):z to range from 1:1 to 1.12:1.In other words, the organic light-emitting layer of Example 1 isconfigured to allow the position of the light emission region inside theorganic light-emitting layer of Example 1 to come closer to the electrontransport layer, as the parameter S′ indicating the molecularorientation degree comes closer to 0.66.

TABLE 6 S′ Organic Light-Emitting Layer of 0.675 Example 1 OrganicLight-Emitting Layer of 0.749 Comparative Example 1

[Effects]

Description is next given of effects of the organic electroluminescencedevice 1 of the present embodiment.

[Detailed Issues]

In recent years, attention has been focused on formation of layers suchas the organic light-emitting layer through a simple manufacturingprocess using coating that enables forming the layers easily at a largearea scale. When forming the layers such as the organic light-emittinglayer using coating, it is necessary to insolubilize an underlayer, forexample. When forming the hole transport layer as the underlayer also bycoating, for example, there may be a method of using a material havingan insoluble function as a constituent material of the hole transportlayer. When using, for the hole transport layer, a material providedwith functions of solubility and insolubilization, however, the materialprovided with the functions of solubility and insolubilizationincorporates, in a molecular structure thereof, a group such as asoluble group, a cross-linking group, and a thermal dissociation solublegroup, and thus conjugation is extended, causing an energy gap to benarrower. Accordingly, particularly the blue organic electroluminescencedevice may have a lowered device performance.

In contrast, in the present embodiment, the light emission region in theorganic light-emitting layer 13 may lie on electron transport layerside. As a result, for example, even when the hole transport layer 12 isa hole transport layer insolubilized with the insoluble function, i.e.,even when the hole transport layer 12 is made of a material having theinsoluble function, deactivation due to the hole transport layer 12 isless likely to occur. Thus, it becomes possible to prevent the deviceperformance from being lowered even in the case of the coated organicelectroluminescence device configured by the hole transport layer 12 asa coated film and the organic light-emitting layer 13 as a coated film.

The energy gap Eg1 in the hole transport layer 12 is substantially equalto the energy gap Eg2 of a dopant contained in the organiclight-emitting layer 13. Thus, there is a case where deactivation mayoccur due to the hole transport layer 12. In the present embodiment,however, the light emission region 13A may lie on electron transportlayer side inside the organic light-emitting layer 13, thus making thedeactivation due to the hole transport layer 12 less likely to occur.Therefore, it becomes possible to prevent the device performance frombeing lowered even when the energy gap Eg1 in the hole transport layer12 is substantially equal to the energy gap Eg2 of the dopant containedin the organic light-emitting layer 13.

At least a portion of the emission spectrum 13 a in the organiclight-emitting layer 13 overlaps the absorption spectrum 12 a in thehole transport layer 12. In the present embodiment, however, the lightemission region 13A may lie on electron transport layer side inside theorganic light-emitting layer 13, thus making the deactivation due to thehole transport layer 12 less likely to occur. Therefore, it becomespossible to prevent the device performance from being lowered even whenat least a portion of the emission spectrum 13 a in the organiclight-emitting layer 13 overlaps the absorption spectrum 12 a in thehole transport layer 12.

In the present embodiment, the light emission region 13A lies onelectron transport layer side. Thus, there is a case where deactivationmay occur due to the electron transport layer 14. In the presentembodiment, however, the electron transport layer 14 may be configuredby a deposited film, thus making it possible to easily select, as theconstituent material of the electron transport layer 14, a materialhaving the energy gap Eg3 that is wider than the energy gap Eg2 in theorganic light-emitting layer 13. Consequently, it becomes possible toprevent the device performance from being lowered, because the energygap Eg3 in the electron transport layer 14 is wider than the energy gapEg2 of the dopant contained in the organic light-emitting layer 13.

The emission spectrum 13 a in the organic light-emitting layer 13 doesnot overlap the absorption spectrum 14 a in the electron transport layer14. Therefore, in the present embodiment, the light emission region 13Alies on electron transport layer side inside the organic light-emittinglayer 13, and thus deactivation due to the electron transport layer 14is less likely to occur. Consequently, it becomes possible to preventthe device performance from being lowered, because the emission spectrum13 a in the organic light-emitting layer 13 does not overlap theabsorption spectrum 14 a in the electron transport layer 14.

In the present embodiment, when the hole current Ih in the organiclight-emitting layer 13 is larger than the electron current Ie in theorganic light-emitting layer 13, the light emission region 13A lies onelectron transport layer side. Therefore, the deactivation due to thehole transport layer 12 is less likely to occur, thus making it possibleto prevent the device performance from being lowered. Further, in thepresent embodiment, when the quotient of the hole current Ih divided bythe electron current Ie is larger than 5, the light emission region 13Alies in the vicinity of an interface with respect to the electrontransport layer. Therefore, the deactivation due to the hole transportlayer 12 is still less likely to occur, thus making it possible tofurther prevent the device performance from being lowered.

In the present embodiment, when the hole mobility μh in the organiclight-emitting layer 13 is larger than the electron mobility μe in theorganic light-emitting layer 13, the light emission region 13A lies onelectron transport layer side. Therefore, the deactivation due to thehole transport layer 12 is less likely to occur, thus making it possibleto prevent the device performance from being lowered. Further, in thepresent embodiment, when the quotient of the hole mobility μh divided bythe electron mobility μe is larger than 10, the light emission region13A lies in the vicinity of an interface with respect to the electrontransport layer. Therefore, the deactivation due to the hole transportlayer 12 is still less likely to occur, thus making it possible tofurther prevent the device performance from being lowered.

In the present embodiment, when the organic light-emitting layer 13 isconfigured to allow the position of the light emission region 13A insidethe organic light-emitting layer 13 to come closer to side where theelectron transport layer is disposed, as the quotient of the holecurrent Ih divided by the electron current Ie becomes larger, thedeactivation due to the hole transport layer 12 is less likely to occur,thus making it possible to surely prevent the device performance frombeing lowered.

In the present embodiment, when the organic light-emitting layer 13 isconfigured to allow the position of the light emission region 13A insidethe organic light-emitting layer 13 to come closer to side where theelectron transport layer is disposed, as the quotient of the holemobility μh divided by the electron mobility μe becomes larger, thedeactivation due to the hole transport layer 12 is less likely to occur,thus making it possible to surely prevent the device performance frombeing lowered.

In the present embodiment, when the parameter S′ indicating themolecular orientation degree in the organic light-emitting material thatconstitutes the organic light-emitting layer satisfies a range largerthan 0.66 and smaller than 0.75 (0.66<S′<0.75), the direction of themolecular orientation of the organic light-emitting material in theorganic light-emitting layer 13 may be determined to allow the ratio ofx (or y):z to range from 1:1 to 1.5:1, where the x-axis and the y-axisare defined as directions orthogonal to each other in the film-planedirection of the organic light-emitting layer 13, and the z-axis isdefined as the film-thickness direction of the organic light-emittinglayer 13.

More preferably, in the present embodiment, the parameter S′ indicatingthe molecular orientation degree in the organic light-emitting materialthat constitutes the organic light-emitting layer may be in a rangelarger than 0.66 and smaller than 0.72 (0.66<S′<0.72). In this case, thedirection of the molecular orientation of the organic light-emittingmaterial in the organic light-emitting layer 13 may be determined toallow the ratio of x (or y):z to range from 1:1 to 1.29:1.

Still more preferably, the parameter S′ may be in a range larger than0.66 and smaller than 0.69 (0.66<S′<0.69). In this case, the directionof the molecular orientation of the organic light-emitting material inthe organic light-emitting layer 13 may be determined to allow the ratioof x (or y):z to range from 1:1 to 1.12:1.

It is presumed that the light emission region is changed due to such adifference in the molecular orientation degree, i.e., the light emissionregion is changed by changing the film property. In the presentembodiment, the orientation of the organic light-emitting material 13Mthat constitutes the organic light-emitting layer 13 is disorderly,i.e., random, and thus the light emission region 13A inside the organiclight-emitting layer 13 lies on electron transport layer side.Therefore, the deactivation due to the hole transport layer 12 is lesslikely to occur, thus making it possible to prevent the deviceperformance from being lowered. Further, in the present embodiment, theorientation of the organic light-emitting material 13M that constitutesthe organic light-emitting layer 13 is disorderly, i.e., random, andthus the light emission region 13A inside the organic light-emittinglayer 13 lies in the vicinity of an interface with respect to theelectron transport layer. Therefore, the deactivation due to the holetransport layer 12 is still less likely to occur, thus making itpossible to further prevent the device performance from being lowered.

In the present embodiment, when the organic light-emitting layer 13 isconfigured to allow the position of the light emission region 13A insidethe organic light-emitting layer 13 to come closer to side where theelectron transport layer is disposed, as the molecular orientationdegree in the organic light-emitting material that constitutes theorganic light-emitting layer becomes more random, in other words, as theparameter S′ comes closer to 0.66 . . . , i.e., ⅔, the deactivation dueto the hole transport layer 12 is less likely to occur, thus making itpossible to surely prevent the device performance from being lowered.

2. Second Embodiment [Configuration]

FIG. 6 illustrates an example of an outline configuration of an organicelectroluminescence unit 2 according to a second embodiment of thedisclosure. FIG. 7 illustrates an example of a circuit configuration ofeach pixel 21 provided in the organic electroluminescence unit 2. Theorganic electroluminescence unit 2 may include, for example, a displaypanel 20, a controller 30, and a driver 40. The driver 40 may be mountedon an outer edge portion of the display panel 20. The display panel 20may include a plurality of pixels 21 that are arranged in matrix. Thecontroller 30 and the driver 40 may each drive the display panel 20 onthe basis of a synchronization signal Tin and an image signal Dininputted from the outside.

(Display Panel 20)

The display panel 20 may display an image on the basis of thesynchronization signal Tin and the image signal Din inputted from theoutside, in response to active-matrix driving performed on each pixel 21by the controller 30 and the driver 40. The display panel 20 may includea plurality of scanning lines WSL and a plurality of power supply linesDSL both extending in a row direction, a plurality of signal lines DTLextending in a column direction, and a plurality of pixels 21 disposedin matrix.

The scanning lines WSL may be each used to select each of the pixels 21.The scanning lines WSL may each supply each of the pixels 21 with aselection pulse to thereby select each of the pixels 21 on apredetermined-unit basis (e.g., on a pixel-row basis). The signal linesDTL may be each used to supply each of the pixels 21 with a signalvoltage Vsig based on the image signal Din. Specifically, the signallines DTL may each supply each of the pixels 21 with a data pulseincluding the signal voltage Vsig. The power supply lines DSL may eachsupply each of the pixels 21 with electricity.

The plurality of pixels 21 may include, for example, a plurality ofpixels 21 that emit red light, a plurality of pixels 21 that emit greenlight, and a plurality of pixels 21 that emit blue light. It is to benoted that the plurality of pixels 21 may further include a plurality ofpixels 21 that emit light of other colors such as white light and yellowlight, for example.

Each of the signal lines DTL may be coupled to an output end of ahorizontal selector 41 described later. For example, the plurality ofsignal lines DTL may be assigned to respective pixel columns. Each ofthe scanning lines WSL may be coupled to an output end of a writescanner 42 described later. For example, the plurality of scanning linesWSL may be assigned to respective pixel rows. Each of the power supplylines DSL may be coupled to an output end of a power supply. Forexample, the plurality of power supply lines DSL may be assigned torespective pixel rows.

Each of the pixels 21 may include, for example, a pixel circuit 21A andan organic electroluminescence device 21B. The organicelectroluminescence device 21B may be, for example, the organicelectroluminescence device 1 of the foregoing embodiment. One or more ofthe plurality of pixels 21 included in the display panel 20 may includethe organic electroluminescence device 1 of the foregoing embodiment. Inother words, one or more of the plurality of organic electroluminescencedevices 21B included in the display panel 20 may be configured by theorganic electroluminescence device 1 of the foregoing embodiment.

For example, each of the pixels 21 that emit blue light may include theorganic electroluminescence device 1 of the foregoing embodiment as theorganic electroluminescence device 21B. For example, each of the pixels21 that emit red light as well as each of the pixels 21 that emit greenlight may include, as the organic electroluminescence device 21B, theorganic electroluminescence device 1 of the foregoing embodiment thatincludes the organic light-emitting layer 113 instead of the organiclight-emitting layer 13. Further, for example, each of the pixels 21that emit red light as well as each of the pixels 21 that emit greenlight may include, as the organic electroluminescence device 21B, theorganic electroluminescence device 1 of the foregoing embodiment thatincludes the organic light-emitting layer 113 instead of the organiclight-emitting layer 13 and the hole transport layer 112 instead of thehole transport layer 112.

The pixel circuit 21A may control light emission and light extinction ofthe organic electroluminescence device 21B. The pixel circuit 21A mayserve to hold a voltage that is written into each of the pixels 21through write scanning described later. The pixel circuit 21A mayinclude, for example, a drive transistor Tr1, a write transistor Tr2,and a holding capacitor Cs.

The write transistor Tr2 may control application of the signal voltageVsig corresponding to the image signal Din, to a gate of the drivetransistor Tr1. More specifically, the write transistor Tr2 may sample avoltage of the signal line DTL and write the sampled voltage into thegate of the drive transistor Tr1. The drive transistor Tr1 may becoupled in series to the organic electroluminescence device 21B. Thedrive transistor Tr1 may drive the organic electroluminescence device21B. The drive transistor Tr1 may control a current that flows throughthe organic electroluminescence device 21B on the basis of the magnitudeof the voltage sampled by the write transistor Tr2. The holdingcapacitor Cs may hold a predetermined voltage between the gate and asource of the drive transistor Tr1. The holding capacitor Cs may serveto allow a gate-source voltage Vgs of the drive transistor Tr1 to beconstant during a predetermined period. It is to be noted that the pixelcircuit 21A either may have a circuit configuration that includescomponents such as various capacitors and various transistors inaddition to the above-described 2Tr1C circuit configuration, or may havea circuit configuration different from the above-described 2Tr1C circuitconfiguration.

The signal lines DTL may be each coupled to an output end of thehorizontal selector 41 described later, and also coupled to one of asource and a drain of the write transistor Tr2. The scanning lines WSLmay be each coupled to an output end of the write scanner 42 describedlater, and also coupled to a gate of the write transistor Tr2. The powersupply lines DSL may be each coupled to an output end of a power supplycircuit 33, and also coupled to one of the source and a drain of thedrive transistor Tr1.

The gate of the write transistor Tr2 may be coupled to corresponding oneof the scanning lines WSL. One of the source and the drain of the writetransistor Tr2 may be coupled to corresponding one of the signal linesDTL. A terminal of the source and the drain of the write transistor Tr2,which is not coupled to any of the signal lines DTL, may be coupled tothe gate of the drive transistor Tr1. One of the source and the drain ofthe drive transistor Tr1 may be coupled to corresponding one of thepower supply lines DSL. A terminal of the source and the drain of thedrive transistor Tr1, which is not coupled to any of the power supplylines DSL, may be coupled to the anode 11 of the organicelectroluminescence device 21B. One end of the holding capacitor Cs maybe coupled to the gate of the drive transistor Tr1. The other end of theholding capacitor Cs may be coupled to a terminal, on organicelectroluminescence device 21B side, of the source and the drain of thedrive transistor Tr1.

(Driver 40)

The driver 40 may include the horizontal selector 41 and the writescanner 42, for example. The horizontal selector 41 may apply to each ofthe signal lines DTL the analog signal voltage Vsig inputted from thecontroller 30, in response to (in synchronization with) reception of acontrol signal, for example. The write scanner 42 may scan the pluralityof pixels 21 on a predetermined-unit basis.

(Controller 30)

Description is next given of the controller 30. The controller 30 mayperform predetermined correction on the digital image signal Dininputted from the outside, thereby generating the signal voltage Vsig onthe basis of an image signal obtained through the predeterminedcorrection, for example. The controller 30 may output the generatedsignal voltage Vsig to the horizontal selector 41, for example. Thecontroller 30 may output a control signal to each of the circuits insidethe driver 40 in response to (in synchronization with) thesynchronization signal Tin inputted from the outside, for example.

[Effects]

In the present embodiment, one or more of the plurality of organicelectroluminescence devices 21B included in the display panel 20 areconfigured by the organic electroluminescence device 1 of the foregoingembodiment. Consequently, it becomes possible to achieve the organicelectroluminescence unit 2 having high light emission efficiency.

3. Application Examples Application Example 1

Description is given below of an application example of the organicelectroluminescence unit 2 described in the foregoing second embodiment.The organic electroluminescence unit 2 is applicable to display units ofelectronic apparatuses in any fields that display, as an image or apicture, an image signal inputted from the outside or an image signalgenerated inside, such as televisions, digital cameras, notebookpersonal computers, sheet-like personal computers, portable terminaldevices such as mobile phones, and video cameras.

FIG. 8 is a perspective view of an appearance of an electronic apparatus3 according to the present application example. The electronic apparatus3 may be, for example, a sheet-like personal computer provided with adisplay surface 320 on a main surface of a casing 310. The electronicapparatus 3 may be provided with the organic electroluminescence unit 2on the display surface 320 of the electronic apparatus 3. The organicelectroluminescence unit 2 may be disposed to allow the display panel 20to face outward. In the present application example, the organicelectroluminescence unit 2 may be provided on the display surface 320,thus making it possible to achieve the electronic apparatus 3 havinghigh light emission efficiency.

Application Example 2

Description is given below of an application example of the organicelectroluminescence device 1 described in the foregoing firstembodiment. The organic electroluminescence device 1 is applicable tolight sources for illumination apparatuses in any fields, such asillumination apparatuses for table lighting or floor lighting, andillumination apparatuses for room lighting.

FIG. 9 illustrates an appearance of an illumination apparatus for roomlighting to which the organic electroluminescence device 1 isapplicable. The illumination apparatus may include, for example, anilluminating section 410 including one or a plurality of organicelectroluminescence devices 1. Appropriate numbers of the illuminatingsections 410 may be provided at appropriate intervals on a ceiling 420of a building. It is to be noted that application of the illuminatingsection 410 is not only limited to the ceiling 420; the illuminatingsection 410 may also be installed on any place such as a wall 430 and anunillustrated floor depending on use application.

In these illumination apparatuses, illumination is performed using lightsupplied from the organic electroluminescence device 1. Thus, it becomespossible to achieve the illumination apparatus having high lightemission efficiency.

Although the disclosure has been described hereinabove by way of examplewith reference to the embodiments and the application examples, thedisclosure is not limited thereto but may be modified in a wide varietyof ways. It is to be noted that the effects described hereinabove aremere examples. The effects according to an embodiment of the disclosureare not limited to those described hereinabove. The disclosure mayfurther include other effects in addition to the effects describedhereinabove.

Moreover, the disclosure may also have the following configurations.

(1) An organic electroluminescence device including, in order:

a first electrode;

a hole transport layer configured by a coated film;

an organic light-emitting layer configured by a coated film;

an electron transport layer; and

a second electrode,

in which the organic light-emitting layer is made of an organiclight-emitting material that has a molecular orientation degreespecified by a parameter S′, the parameter S′ satisfying the followinginequality:

0.66<S′<0.75, provided that

S′={(2×ko)/(ke+2ko)}

where ko denotes an extinction coefficient in a film-plane direction ofthe organic light-emitting layer, and ke denotes an extinctioncoefficient in a film-thickness direction of the organic light-emittinglayer.

(2) The organic electroluminescence device according to (1), in whichthe parameter S′ satisfies an inequality: 0.66<S′<0.72.

(3) The organic electroluminescence device according to (2), in whichthe parameter S′ satisfies an inequality: 0.66<S′<0.69.

(4) The organic electroluminescence device according to any one of (1)to (3), in which a position of the light emission region provided in theorganic light-emitting layer comes closer to the electron transportlayer, as the parameter S′ comes closer to 0.66.

(5) The organic electroluminescence device according to any one of (1)to (4), in which the hole transport layer includes an insolubilized holetransport layer.

(6) The organic electroluminescence device according to (5), in whichthe electron transport layer has an energy gap that is larger than anenergy gap of the organic light-emitting layer.

(7) The organic electroluminescence device according to (6), in whichthe electron transport layer includes a deposited film.

(8) An organic electroluminescence unit provided with a plurality oforganic electroluminescence devices, one or more of the plurality oforganic electroluminescence devices including, in order:

a first electrode;

a hole transport layer configured by a coated film;

an organic light-emitting layer configured by a coated film;

an electron transport layer; and

a second electrode,

in which the organic light-emitting layer is made of an organiclight-emitting material that has a molecular orientation degreespecified by a parameter S′, the parameter S′ satisfying the followinginequality:

0.66<S′<0.75, provided that

S′={(2×ko)/(ke+2ko)}

where ko denotes an extinction coefficient in a film-plane direction ofthe organic light-emitting layer, and ke denotes an extinctioncoefficient in a film-thickness direction of the organic light-emittinglayer.

(9) An electronic apparatus provided with an organic electroluminescenceunit, the organic electroluminescence unit having a plurality of organicelectroluminescence devices, one or more of the plurality of organicelectroluminescence devices including, in order:

a first electrode;

a hole transport layer configured by a coated film;

an organic light-emitting layer configured by a coated film;

an electron transport layer; and

a second electrode,

in which the organic light-emitting layer is made of an organiclight-emitting material that has a molecular orientation degreespecified by a parameter S′, the parameter S′ satisfying the followinginequality:

0.66<S′<0.75, provided that

S′={(2×ko)/(ke+2ko)}

where ko denotes an extinction coefficient in a film-plane direction ofthe organic light-emitting layer, and ke denotes an extinctioncoefficient in a film-thickness direction of the organic light-emittinglayer.

According to the organic electroluminescence device, the organicelectroluminescence unit, and the electronic apparatus of the respectiveembodiments of the disclosure, the organic light-emitting layer is madeof an organic light-emitting material that has a molecular orientationdegree specified by the parameter S′. The parameter S′ satisfies aninequality: 0.66<S′<0.75, thus making it possible to enhance the deviceperformance of the organic electroluminescence device. It is to be notedthat the foregoing technical contents are mere examples of thedisclosure. The effects according to an embodiment of the disclosure arenot limited to those described hereinabove. The disclosure may haveeffects different from those described hereinabove, or may furtherinclude other effects in addition to those described hereinabove.

Although the technology has been described in terms of exemplaryembodiments, it is not limited thereto. It should be appreciated thatvariations may be made in the described embodiments by persons skilledin the art without departing from the scope of the technology as definedby the following claims. The limitations in the claims are to beinterpreted broadly based on the language employed in the claims and notlimited to examples described in this specification or during theprosecution of the application, and the examples are to be construed asnon-exclusive. For example, in this disclosure, the term “preferably” orthe like is non-exclusive and means “preferably”, but not limited to.The use of the terms first, second, etc. do not denote any order orimportance, but rather the terms first, second, etc. are used todistinguish one element from another. The term “about” as used hereincan allow for a degree of variability in a value or range. Moreover, noelement or component in this disclosure is intended to be dedicated tothe public regardless of whether the element or component is explicitlyrecited in the following claims.

What is claimed is:
 1. An organic electroluminescence device comprising,in order: a first electrode; a hole transport layer configured by acoated film; an organic light-emitting layer configured by a coatedfilm; an electron transport layer; and a second electrode, wherein theorganic light-emitting layer is made of an organic light-emittingmaterial that has a molecular orientation degree specified by aparameter S′, the parameter S′ satisfying the following inequality:0.66<S′<0.75, provided thatS′={(2×ko)/(ke+2ko)} where ko denotes an extinction coefficient in afilm-plane direction of the organic light-emitting layer, and ke denotesan extinction coefficient in a film-thickness direction of the organiclight-emitting layer.
 2. The organic electroluminescence deviceaccording to claim 1, wherein the parameter S′ satisfies an inequality:0.66<S′<0.72.
 3. The organic electroluminescence device according toclaim 2, wherein the parameter S′ satisfies an inequality: 0.66<S′<0.69.4. The organic electroluminescence device according to claim 1, whereina position of the light emission region provided in the organiclight-emitting layer comes closer to the electron transport layer, asthe parameter S′ comes closer to 0.66.
 5. The organicelectroluminescence device according to claim 1, wherein the holetransport layer comprises an insolubilized hole transport layer.
 6. Theorganic electroluminescence device according to claim 5, wherein theelectron transport layer has an energy gap that is larger than an energygap of the organic light-emitting layer.
 7. The organicelectroluminescence device according to claim 6, wherein the electrontransport layer comprises a deposited film.
 8. An organicelectroluminescence unit provided with a plurality of organicelectroluminescence devices, one or more of the plurality of organicelectroluminescence devices comprising, in order: a first electrode; ahole transport layer configured by a coated film; an organiclight-emitting layer configured by a coated film; an electron transportlayer; and a second electrode, wherein the organic light-emitting layeris made of an organic light-emitting material that has a molecularorientation degree specified by a parameter S′, the parameter S′satisfying the following inequality:0.66<S′<0.75, provided thatS′={(2×ko)/(ke+2ko)} where ko denotes an extinction coefficient in afilm-plane direction of the organic light-emitting layer, and ke denotesan extinction coefficient in a film-thickness direction of the organiclight-emitting layer.
 9. An electronic apparatus provided with anorganic electroluminescence unit, the organic electroluminescence unithaving a plurality of organic electroluminescence devices, one or moreof the plurality of organic electroluminescence devices comprising, inorder: a first electrode; a hole transport layer configured by a coatedfilm; an organic light-emitting layer configured by a coated film; anelectron transport layer; and a second electrode, wherein the organiclight-emitting layer is made of an organic light-emitting material thathas a molecular orientation degree specified by a parameter S′, theparameter S′ satisfying the following inequality:0.66<S′<0.75, provided thatS′={(2×ko)/(ke+2ko)} where ko denotes an extinction coefficient in afilm-plane direction of the organic light-emitting layer, and ke denotesan extinction coefficient in a film-thickness direction of the organiclight-emitting layer.